1. Field of the Invention
The present invention relates to an accommodating intraocular lens to be implanted in a lens capsule (or a capsular bag) of human or natural eye in a surgical procedure subsequent to extracapsular cataract extraction. In particular, the invention is directed to a novel intraocular ring assembly and a novel artificial lens kit for implantation in the lens capsule or capsular bag, which are designed to enable the eye to have an optimal accommodation to gain near and distant visions.
2. Description of Prior Art
A human eye has a crystalline lens which is endowed with accommodation, i.e. a natural focal function in the lens to adjust its focus on an object being moved from a far distance to a nearby distance, or vice versa, so that a human being with the eyes can keep a dear vision for the moving object.
It is generally believed that the accommodation of human eye is based on the following actions: When the eye gazes at an object located at a far distance, a crystalline lens in the eye, which substantially serves as an artificial optical lens, is kept in a flattened state. Now, when the eye changes its gazing from the object at a far distance to a new object located at a nearby distance, a circular ciliary muscle (a circular muscle of ciliary body (at 50 in FIG. 21)) circumscribing the crystalline lens is contracted to cause relaxation of zonule of Zinn (see the designation 42 in FIG. 21), because of the lens being connected via the zonule (plural thin fibrous tissues) with a ciliary body (at 50 in FIG. 21). Such relaxation of zonule allows the crystalline lens to become inflated into a spherical shape, increasing its thickness, due to the inherent elastic expansive property of the lens, whereby the refractive power of the lens is increased so as to properly adjust a focus on the object at near distance, thus attaining a clear vision thereof.
By contrast, when the eye changes its gazing from the nearby object to a far distant object, the actions are reversal: the circular ciliary muscle mentioned above is then relaxed to cause traction of the crystalline lens via the zonule, thereby stretching the crystalline lens outwardly, with the result that the lens is transformed into a flattened shape from the spherical shape, thus decreasing the refractive power of the lens so as to properly adjust focus on the far distant object.
The crystalline lens is normally transparent, but, for some reasons or other, the lens itself is subjected to opacification. In that case, a light entering the eye is scattered by the opacified crystalline lens before reaching a retina, and therefore, a precise image can hardly be formed at the retina or fundus, which results in a misted or dim vision. In most cases, this symptom is what is generally known as “cataract”. The nature of the cataract varies according to different causes, such as an age-related cataract, a congenital cataract, a diabetic cataract, a traumatic cataract, and a glass-blower's cataract due to an occupational disease caused by exposure to infrared rays. Recent years witness an increased number of cataract patients.
A brief explanation will be made as to the crystalline lens. Crystalline lens is in the form of a biconvex lens and has a transparent outer thin capsular membrane with an elastic property, which covers the entirety of an inner lens matrix. Such capsular outer membrane is what is referred to as “lens capsule”. Ophthalmologically stated, the lens capsule is divided into a forward portion facing to a cornea (see the designation 52 in FIG. 21); i.e. what is referred to as “anterior capsule”, and a rearward portion facing to a vitreous (see the designation 53 in FIG. 21); i.e. what is referred to as “posterior capsule”.
The boundary between those anterior and posterior capsules is the so-called “equator” which expends along the outer circumference of the lens capsule. Integrally fixed to the periphery of the lens capsule substantially corresponding to the equator is the zonule which connect the crystalline lens and the ciliary body.
Typical treatment for the foregoing crystalline lens disease, or the cataract, includes an intraocular lens implantation to replace an opacified natural lens. This sort of procedure normally entails the steps of making an incision to the anterior capsule of the lens to form a circular opening therein, then extracting an inner matrix from the lens capsule via such circular opening to leave an empty capsule or the so-called capsular bag, and thereafter, implanting an intraocular lens in that capsular bag.
Conventional intraocular lenses, however, do not provide a sufficient accommodation since they are incapable of increasing and decreasing the thickness of the lens itself, and do not insure a precise forward and backward movement of the lens in the direction anteriorly and posteriorly of eye. Yet, almost all of the conventional intraocular lenses are not designed to gain an optimum focus on near and distant objects, and, in most cases, they still rely on a fixed focus, resulting in a wearer of the intraocular lenses requiring eyeglasses. As a consequence thereof, it can be mentioned that the conventional intraocular lenses can not work with ciliary body and zonule to a satisfactory degree, and therefore, have not yet achieved an optimum focus on every object located at near or far distance, raising the problem that the lens wearer can not have a satisfactory clear vision for various objects at all ranges of distances and will encounter any unexpected inconvenience and trouble postoperatively.